This invention relates to a method for producing a color-separation film in accordance with a printing plate fabrication technique making use of a color scanner, in which the color-separation film includes both the picture being scanned and a mask region serving as an outlining mask which is required in a subsequent treatment step, the mask region being formed on the color-separation film concurrently with the recordation of the picture.
In recent processes for producing printing plates, preparation steps such as machine plate preparation steps and block copy preparation steps have been required. Layout scanners which can achieve electronic performance of most of such steps have been finding utility in some areas.
The conventional process is, however, still in wide use. In this process, color-separation pictures are produced by means of a color scanner, after which they are pasted up and assembled by manual and contact exposure work respectively.
To make the pasting-up and assembly work simpler, original color pictures are sometimes pasted up on a layer sheet in accordance with the desired layout pattern so as to provide a pasted-up original color page picture. The original color page picture is then scanned by means of a color scanner so as to color-separate the compound color page picture as a whole (see, for example, Japanese Unexamined Patent Publication (Kokai) No. 59-226348.
FIG. 5 illustrates a process for producing a printing plate by making use of the conventional multiple exposure and printing technique. Original picture patterns B.sub.1, B.sub.2, B.sub.3, which require color separation and halftone photography are pasted up on the layout sheet C in accordance with the desired layout pattern. The sheet C is then mounted on an input cylinder A. The original picture patterns B.sub.1, B.sub.2, B.sub.3 are subjected to color separation and halftone photography and recorded with the same dimensions as a halftone negative on a recording film E mounted on a recording cylinder D to produce a picture pattern negative E'.
For the original picture patterns B.sub.1, B.sub.2, B.sub.3, it is possible to use an intermediate picture which has in advance been reproduced, with a magnification designated upon preparation of a layout pattern, on a color duplicate film or color photographic paper from an original such as color film or the like by means of a duplicate camera. At this time, in order to facilitate simultaneous processing by a color scanner, original picture patterns to be pasted up on a common pasting-up layout sheet C (e.g., a transparent film or white paper sheet which may optionally be equipped with registration marks or the like as desired) are subjected to balancing such as gradation.
In order to assemble characters, line pictures and/or the like together with the picture patterns on a layout sheet C, it is necessary to prepare a negative (F) which includes both line pictures and a line picture block copy of these characters and a trimming layout mask G which includes trimming regions for the picture patterns (the trimming regions being rendered transparent at the location of the windows corresponding to the position of the pictures B.sub.1, B.sub.2, B.sub.3 and the remaining parts being rendered opaque). Thereafter, the picture pattern negative E' and the layout mask G are placed in registration and contact exposed to form a film H which is then contact exposed with the line picture negative F so as to obtain a finished positive J.
This multiple contact exposure process requires correct positioning and registration of the various films. When it is necessary to obtain a layout making the boundaries of the picture patterns hardly noticeable, a high degree of accuracy is indispensable in positioning and registering a plurality of masking patterns relative to one another.
As an alternative process, intermediate pictures are produced respectively from originals on color duplicate films, the intermediates are cut into sizes which conform with their corresponding desired trimming frames, the thus-cut intermediates are pasted up on a transparent sheet, the transparent sheet is wrapped on an original cylinder with the originals in contact with the circumferential outer wall of the original cylinder, and the originals are then scanned.
The above process is however accompanied by a practical drawback that considerable difficulties are encountered upon cutting the desired trimming regions of the intermediates precisely in accordance with desired trimming sizes. It is also accompanied by an inconvenience that the process has to be repeated from the preparation of intermediates when the desired trimming frames are changed after color separation.
In Japanese Unexamined Patent Publication (Kokai) No. 59-226348 the present applicant has disclosed to prepare a color-separation film by recording and exposing picture patterns bearing not only characters and/or line pictures but also necessary rectangular masks on rectangular trimming regions.
However, Japanese Unexamined Patent Publication (Kokai) No. 59-226348 does not disclose anything about the recording of picture patterns with masks of desired shapes.